refactor: migrate DI to Wire, replace startup registries with on-demand DB queries

- Add google/wire; generate wire_gen.go from wire.go injector
- Move all constructor wiring out of main.go into providers.go / wire.go
- Export recognition.IngredientRepository (was unexported, blocked Wire binding)
- Delete units/cuisine/tag registry.go files (global state + unused NameFor helpers)
- Replace List handlers with NewListHandler(pool) using COALESCE SQL queries
- Remove units/cuisine/tag LoadFromDB from server startup; locale.LoadFromDB kept
  (locale.Supported is used by language middleware on every request)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/server/server.go

@@ -5,7 +5,6 @@ import (
 	"net/http"
 
 	"github.com/food-ai/backend/internal/auth"
-	"github.com/food-ai/backend/internal/cuisine"
 	"github.com/food-ai/backend/internal/diary"
 	"github.com/food-ai/backend/internal/dish"
 	"github.com/food-ai/backend/internal/home"
@@ -14,8 +13,6 @@ import (
 	"github.com/food-ai/backend/internal/menu"
 	"github.com/food-ai/backend/internal/middleware"
 	"github.com/food-ai/backend/internal/recipe"
-	"github.com/food-ai/backend/internal/tag"
-	"github.com/food-ai/backend/internal/units"
 	"github.com/food-ai/backend/internal/product"
 	"github.com/food-ai/backend/internal/recognition"
 	"github.com/food-ai/backend/internal/recommendation"
@@ -41,6 +38,9 @@ func NewRouter(
 	recipeHandler *recipe.Handler,
 	authMiddleware func(http.Handler) http.Handler,
 	allowedOrigins []string,
+	unitsListHandler http.HandlerFunc,
+	cuisineListHandler http.HandlerFunc,
+	tagListHandler http.HandlerFunc,
 ) *chi.Mux {
 	r := chi.NewRouter()
 
@@ -54,9 +54,9 @@ func NewRouter(
 	// Public
 	r.Get("/health", healthCheck(pool))
 	r.Get("/languages", language.List)
-	r.Get("/units", units.List)
-	r.Get("/cuisines", cuisine.List)
-	r.Get("/tags", tag.List)
+	r.Get("/units", unitsListHandler)
+	r.Get("/cuisines", cuisineListHandler)
+	r.Get("/tags", tagListHandler)
 	r.Route("/auth", func(r chi.Router) {
 		r.Post("/login", authHandler.Login)
 		r.Post("/refresh", authHandler.Refresh)